Currently the majority of methods used to estimate paleo-elevation are
based on the relationship of temperature with altitude, and for this
reason, are inherently climate-sensitive. It remains difficult
therefore to decipher the effects of changing elevation and broad
scale global climatic change on these paleo-altimeters, which
critically hampers our ability to evaluate or constrain theories
relating to tectonic and climatic evolution. The reduction in
CO2 partial pressure with altitude exerts a physiological
limitation on plant photosynthesis, which is compensated for, in many
species, by an increase in stomatal frequency (density and index) and
altered stomatal distribution. This strong inverse relationship
between stomatal frequency and atmospheric CO2
concentration, which has been repeatedly demonstrated experimentally
and historically over the past 200 years of anthropogenic
CO2 rise, has been successfully utilized to reconstruct
paleo-CO2 concentrations on timescales of centuries to
millennia. The accuracy with which paleo-CO2 concentrations
can be estimated from sub-fossil and fossil stomata, and the
observation that stomatal density and index increase with decreasing
CO2 partial pressure with altitude, now offers the exciting
potential of utilizing this relationship as a novel paleo-altimeter. A
model for estimating paleo-elevation from fossil stomatal frequency
will be presented and the implications of this new method discussed.